In the ABUS Padlocks and Security Products Catalog 101, pages 5 through 8, see especially page 7, a padlock of the aforedescribed type has been illustrated.
Such a lock generally comprises a lock body and a shackle having a pair of shanks connected by a bight, and receivable in this body. Locking means are, of course, provided in the body to engage the shackle and can be released by a cylinder rotatable by a key and extending into the body from its opposite side.
More particularly, the lock body can have a pair of bores opening at one end face of the body, a longer one of these bores receiving a longer shank of the shackle and a shorter one of the bores receiving the shorter shank of the body.
Close to this face of the body, the latter can be formed with a transverse bore which can have the same diameter of the shackle bores and which opens into the shackle bores and can terminate in a constriction at the short shackle bore.
As part of the locking mechanism for the shackle, a pair of balls can be received in the transverse bore and both of the shackles can have transverse grooves or notches turned toward the transverse bore to enable the balls to engage in these notches in the locked position of the shackle.
In addition, the longer shank of the shackle can have a flat extending from its notch in the direction of its free end and which is shallower than the depth of the notch. This allows, with the respective ball extending partly into the longer bore, the shackle to be pulled out of the lock body by a distance corresponding substantially to the length of that axially extending flat. The latter can terminate in a circumferential groove into which the ball can engage to permit free rotation of the long shank in its outer position with the ball engaging therein. The depth of this groove can correspond to the depth of the flat and the free end of the long shank can be a cylinder stop free from axially extending grooves and channels.
The lock body is formed as well with a pair of parallel offset bores receiving a lock cylinder having the general cross section of a FIG. 8 and opening at the opposite end face of the body. Of these bores, the central bore is longer than the other bore and reaches substantially to the transverse bore within the lock body. The offset shorter bore terminates substantially at the blind end of the shorter shank bore so that a screw passing through the bottom of the latter can engage the cylinder and hold the same in place.
In the longer central bore, a cylindrical pin is provided substantially at the intersection of this longer bore with the transverse bore and is rotatable in the longer central bore.
The pin has two opposite axially directed grooves with cylindrical surfaces to receive in part the two balls mentioned previously. One smooth end of the pin rests against the bottom of the longer central bore while the other end face is formed with at least one entraining formation which cooperates with a corresponding entrainer on the juxtaposed end face of the cylinder inserted into that central bore.
When a key is inserted into the cylinder, the latter can be rotated from its locking position or closed position into the open position whereby the entrainer of the cylinder engages the entrainer of the pin and rotates the pin into a position in which the grooves thereof are oriented in line with the transverse bore and the balls can be partly received in these grooves. In this position, the balls are cammed into the grooves of the post from the respective notches of the shanks of the shackle and the shackle can be unlocked. The key can rotate the cylinder in the opposite direction without rotation of the pin and entrainment thereby of the cylinder while one ball disposed between the respective groove of the pin and the flat or the circumferential groove of the longer shank prevents rotation of the pin. Rotation of the pin is therefore permitted again only after the shackle has been fully inserted into its locked position.
A coil spring under the long shank can bias the shackle into its open position.
The pin itself may be biased angularly by a spring so that the displacement of the pin from the locking position into the open position can be effected by this spring.
When a lock provided with such spring is opened by rotation of the key, the shackle springs out by the expansion of the spring below the longer shackle shank.
With a commercially available lock of this type, there is no so-called locking force which could cause the cylinder to return from the open position to the closed position and enable the key to be withdrawn. This is a result of angular play between the entrainers of the pin and the cylinder which allows a return rotation of the cylinder without a forced rotation of the pin.
This can be disadvantageous in many cases since it makes it possible for the user to rotate the cylinder manually into the closed position and withdraw the key without the necessity of closing the lock, i.e. force the shackle back into its locking position. The user can then forget that the padlock has not been locked and may assume that it has been locked because he or she is in possession of the key.
In many cases, it is desirable and, indeed, essential to provide a padlock of this type so that it has forced locking and enables the key to be withdrawn only when the shackle has been returned to its locking position. Such a force locking function is frequently referred to as "key retaining" because it is associated with the inability to withdraw the key unless the shackle is closed.
There are, of course, locks in which such forced locking occurs but such locks are frequently relatively complicated and cannot be used as so-called automatic locks without forced locking as the user may desire.